Intramolecular Ring–Chain Equilibrium Elimination
Strategy for Pinpointing CC Positional and Geometric Isomers
of N‑Alkylpyridinium Unsaturated Fatty Acid
Derivatives via Ion Mobility-Mass Spectrometry
posted on 2024-01-23, 10:29authored byYuling Li, Jiahui Bai, Kuofeng Tseng, Xiaoqiang Zhang, Li Zhang, Jing Zhang, Wenjian Sun, Yinlong Guo
Free unsaturated fatty acids (UFA)
are key intermediates of lipid
metabolism and participate in many metabolic pathways with specific
biological functions. Although various fragmentation-based methods
for pinpointing CC locations in UFA were developed, the current
mass spectrometry methods are difficult to simultaneously differentiate
geometric isomers and positional isomers in trace samples due to low
ionization efficiency, low conversion, and low resolution. Herein,
an intramolecular ring–chain equilibrium elimination strategy
via 4-plex stable isotope labeling dual derivatization-assisted ion
mobility-mass spectrometry was developed, thereby one-pot specifically
labeling CC and carboxyl groups among the trace and unstable
UFA with high sensitivity, high efficiency, and good substrate generality.
It achieved fast separation of both CC positional and geometric
isomers with high resolution, which benefited from eliminating the
intramolecular ring–chain equilibrium by suppressing the formation
of salt bridges between free carboxyl groups and pyridine cations.
4-plex stable isotope labeling reagents showed similar reactivity,
enabling high-throughput quantitative analysis of omics. This method
was successfully applied for accurate and rapid identification of
the UFA composition in olive oil extract. These results suggest that
the developed method provides new insight for rapid characterization
of UFA CC positional and geometric isomers in complex samples
to explore disease biomarkers and food quality control indicators.